Category: Python

Here’s how to compute true positives, false positives, true negatives, and false negatives in Python using the Numpy library.

Note that we are assuming a binary classification problem here. That is a value of 1 indicates a positive class, and a value of 0 indicates a negative class. For multi-class problems, this doesn’t really hold.

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Here’s how to debug your code when using a Jupyter/iPython notebook.

Use Tracer()(). Here’s an example using a simple function (based on this lucid explanation).

 
def test_debug(y):
    x = 10
    # One-liner to start the debugger here.
    from IPython.core.debugger import Tracer; Tracer()() 
    x = x + y 	 
 
    for i in range(10):
        x = x+i
 
    return x
 
test_debug(10)

When the debugger reaches the Tracer()() line, a small line to type in commands will appear under your cell.

Simply type in the variable names to check the values or run other commands. Below I’ve listed some practical Python PBD commands. More can be found here.
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So I wanted to to add an IPython notebook within a WordPress blog post. The first thing I tried was exporting directly to HTML, and copying the HTML directly within the WordPress post. This sort of worked. However, it was very slow to copy all the HTML into the post and the formatting looked terrible.

Then I came across a way to do so, which you can read about here.

The basic idea from above is to export the IPython notebook to HTML, upload it somewhere on your site, and then use an “iframe” to embed the IPython notebook HTML within the WordPress blog post. The author of the above then wrote some javascript to handle sizing issues.

However, I did not want people to be able to directly access the IPython notebook HTML page (if say google indexed it). Rather I want to direct people to the actual WordPress post.

So in the end, I simply add some javascript to the IPython notebook to redirect to the WordPress blog post.

Here are the steps to add an IPython notebook to a WordPress blog post:
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So you want to run the IPython Notebook… and you’re using Anaconda 2.1.0 on some version of Linux.

You are already able to run ipython successfully…

$ ipython
IPython 2.2.0 -- An enhanced Interactive Python
[1]: exit()

But from the command line, when you try to run the IPython Notebook:

$ ipython notebook

You get a bunch of errors… something about sockets. The last error sticks out…

...
    return getattr(self._sock,name)(*args
error: [Errno 99] Cannot assign requested address

A bit of googling shows you some relevant links:

We summarize the two steps needed to get the Anaconda IPython Notebook working here.
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